Ok, I found something. After “Connect” to my Marvel 2.0 with the laptop, initially, when playing music, I get a “connect/disconnect” situation alternatively about every 2 seconds, while the music is playing - sort of staccato on and off.

I clicked on the “speaker” icon in the tray and up popped three options - play directly on the laptop, play on “headset”, and play on “headphones”. I chose the other option than the one it was on and hey presto, the music source stayed connected normally.

Must be two different Bluetooth protocols or some such and the Marvels only work with one of them.